LCD Motion Artifacts 101: Introduction

Illustrations of different motion artifacts that affect clarity of moving objects on LCD displays, using the TestUFO Ghosting Test. The UFO objects were moving horizontally at 960 pixels per second on a 60 Hz LCD, and captured using a pursuit camera.

Ghosting

Ghosting is a trailing motion artifact. It is caused by asymmetric pixel transitions: Transitions from between two colors can be faster in one direction than the other direction. This motion artifact appears only on trailing edges; observe the yellow dome.

PWM Artifacts

PWM artifacts look like repeated images, and can affect motion fludity. PWM represents Pulse-Width Modulation, a technique that many LCD backlights use for dimming screen brightness. Motion artifacts can appear at dim brightness settings. The above photograph was taken during Brightness setting of 0%. See TFTCentral PWM.

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How Were These Images Captured?

Stationary Camera: Capture of Pixel Transitions

A stationary camera is good for photographing pixel transitions statically. However, it is not a very accurate representation of perceived display motion blur and motion artifacts:

Example: Stationary camera photo of a moving object on a display.

Pursuit Camera: Accurate Capture of LCD Motion Artifacts

Pursuit camera are used by display manufacturers for testing (e.g. MPRT pursuit cameras). This is simply a camera that follows on-screen motion. These expensive cameras are extremely accurate at measuring motion blur and other artifacts, since they simulate the eye tracking motion of moving eyes.

However, Blur Busters has developed an inexpensive pursuit camera method which operates in conjunction with the Blur Busters UFO Motion Tests. It makes possible accurate photography of motion artifacts. The test at www.testufo.com/ghosting was used to take the pictures on this page. Blur Busters is the world’s first blog to utilize a pursuit camera for accurate capture of motion artifacts, in WYSIWYG format, as seen by the human eye.

With what shutter speed do make the stationary photograph? I have an ‘old’ Synchmaster 2343BW and want to buy something better. If i photograph at 1/60 i see 1 or 2 ufo’s, when i look at the screen i see 1 ufo and one shadow.

Yes, they are different, with different causes. They can all overlap each other (e.g. ghosting combined with eye-tracking-based motion blur), but they all have different causes.

Except, streaking is the same thing as ghosting — but the word is usually used to describes extreme cases of ghosting where the ghosting trail is very, very long (several refreshes long). Eventually, will need to obtain a very old LCD, or an overclockable LCD, and capture the streaking effect.